اردیبهشت 90 - همه جوره

همه جوره

دانش فراگیرید ؛ چرا که در تنهایی، همدم و در غربت، همره و در خلوت، هم صحبت است . [امام علی علیه السلام]

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لوگوی وبلاگ

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بازدید امروز :8
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کل بازدید :14995
تعداد کل یاداشته ها : 11
03/10/18
6:13 ع

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NA.GH[79]

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بایگانی وبلاگ

اسفند 88[1] اردیبهشت 90[5]

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عاشق آسمونی فانوسهای خاموش جیغ بنفش در ساعت 25 نوری چایی_بیجار مذهب عشق مرجع اس ام اسSMS امپراتوری هخامنشیان ME&YOU شرکت نمین فیلتر دریچه در فراق گل نرگس درختری از جنس باران

عناوین یادداشتهای وبلاگ

Hadrese file injast bardar salam shirin jan 70هستش 69هستش عناوین یادداشتها[11]

67هستش.

NA.GH

Is there some where in our atmosphere where the air temperature can be exceedingly high (say above 500 c or 900 f)yet a person might feel extremely cold .There is a region but is s not at the earth s suface.
You may recall from Chapter that in the upper of our atmosphere ( in the middle and upper therm osphere) air temperatures may exceed 500 c . How ever a thermometer shielded from the sun in this region of the atmosphere would indicate an exltremely low temperature.This apparent discrepancy lies in the meaning of air temperature and how we measure it.
In Chapter 2 we learned that the air temperature is directly related to the average speed at which the air molecules are moving –faster speeds correspond to higher temperatures.In the middle and upper thermosphere air molecules are zipping about at speeds corresponding to extremely high temperatures.However in odere to transfer enough to heat something up by conduction (exposed skin or a thermometer bulb); an extremely large number of molecules must collide with the .In the ;thin; air of the upper atmosphere ;air molecules are moving extraordinarily fast but there are simply not enough of them bouncing against the thermometer bulb for it to register a high temperature .In fact when
properly shielded from the sun the thermometer bulb loses far more energy than it receives and indicates a temperature near absolute zero.
This explains why an astronaut when space walking will not only survive temperatures exceeding 500 c but will also feel a profound coldness when shielded from the sun s radiant energy.At these high altitudes the traditional meaning of air temperature (that is regarding how ;hot; or ;cold something feels)is no longer applicable.
By the body must be equal to the heat it loses surroundings .There is therefore a constant exchange of heat –especially at the surface of the skin –between the body and the environment.
One way the body loses heat is by emitting infrared energy. But wenot only emit radiant energy ;we absorb it as well. Another way the body loses and gaings heat is by conduction and convection;which transfer heat to and from the body by air motions.On a cold day a thin layer of warm air molecules forms close to the shin protecting it from the surrounding cooler air and from the rapid transfer of heat .Thus ; in cold weather when the air is calm the temperature we perceive- called the sensible temperature –is often higher than a thermometer might in dicate. (Could the opposite effect occur where the air temperature is very high and a person might feel exceptionally cold?If you are unsure read the focus section above).
Once the wind starts to blow the insulating layer of warm air is swept away;and heat is rapidly removed from the skin by the constant bombardment of cold air when all other factors are the same the faster the wind blows the greater the heat loss is usually expressed. As a wind –chill factor. The wind –chill charts (Tables 3.2and3.3)translate the ability of the air to take heat away from the human body with wind (it s cooling power)in to a wind –chill equivaent temperature with no wind.For example notice that in Table 3.2an air temperature of 20 f with a wind speed of 30mi/hr produces a wind –chill equivalent temperature of -18 f .This means that exposed skin would lose as much heat in one minute in air with a temperature of 20 f and a wind speed of 30 mi/hr as it would in calm air with a temperature of -18 f .Of course how cold we feel actually depends on a number of factores; including the fit and type of clothing we wear and the amount of exposed skin.
High winds in below –freezing air can remove heat from exposed skin so quickly that the skin may actually freeze and discolor.The freezing of skin called frostbite usually occurs on the body extremities first because they are the greatest distance from the source of body heat.

90/2/3::: 3:32 ع

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66 هستش!!!!!!!!!!!!

NA.GH

FIGURE3.12/mean annual total heating degree-days in thousands of f ;where the number 4on the map represents 4000(base 65 f ) FIGURE3.13 mean annual total cooling degree-days in thousands of f Where the number 1on the map represents 1000(base 65 f) AIR TEMPERATURE AND HUMAN COMFORT probably evreyone realizes that the same air temperature can feel differently on different occasions. For example a temperature of 20 c (68 f) on a clear windless March afternoon in new york city can almost feel balmy after a long hard winter .Yet this same temperature may feel uncomfortably cool on a summmmer afternoon in a stiff breeze. The human bodys perception of temperature ob-viously changes with varying atmospheric conditions The reason for these changes is related to how we ex-change heat energy with our environment. The body stabilizes its temperature primarily by converting food in to heat (metabolism).To maintain a constant temperature the heat produced and absorbed*

90/2/3::: 11:24 ص

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65 هستش

NA.GH

Dily temperaature drops below 65 f. Therefore heating degree-day are determined by subtracting the mean temperature for the day from 65 f. Thus if the mean temperature for a day is 64 f;there would be 1 heating degree –day on this day. On days when the mean temperature is above 65 f;there are no heating degree-days .Hence the lower the average daily temperature the more heating degree –days and the greater the predicted consumption of fuel. When the number of heating degree-days for a whole year is calculated the heating fule requirements for any location can be estimated.Figure 3.12 shows the yearly average number of heating degree-days in various locations throughout the United states. As the mean daily temperature climbs above 65 f people begin to cool their indoor environment .conse quently an index called the cooling degree-day is used during warm weather to estimate the energe needed to cool indoor air to a comfortable level.The forecast of mean daily temperature is converted to cooling degree-days by subtracting 65 f from the mean .The remaining value is the number of cooling degree-days for that day.For exampel a day with a mean temperature of 70f would correspond to (70-65)or 5 cooling degree-days. High values indicate warm weather and high power production for cooling (see fig 3.13). Knowledge of the number of cooling degree-days in an area allows a builder to plan the size and type of equipment that should be installed to provide adequate air conditioning.Also the forecasting of cooling degree –days during the summer gives power companies a way of predicting the energy demand during peak energy periods.A composite of heating plus cooling degree –days would give a practical indication of the energy requirements over the year.Farmers use an index called growinng degree-days as a guide to planting and for determining the approxi mate dates when a crop will be ready for harvesting .A growing degree –day for a particular crop is defind as a day on which the mean daily temperature is one degree above the base temperature (also known as the zero temperature)-the minimum temperature required for growth of that crop. For sweet corn the base temperature is 50 f and for peas it is 40 f . One a summer day in lowa the mean temperature might be 80 f . From table 3.1 we can see that on this day sweet corn would accumulate (80-50)or 30 grow ing degree –days. Theoretically sweet corn can be harvested when it accumulates a total of 2200growing degree –days .So if sweet corn is planted in early April and each –days thereafter averages about 20 growing degree –days the corn would be ready for harvest abiut 110 days later or around the middle of July. At one time corn varieties were rated in terms of days to maturity .This rating system was unsuccessful because in actual practice corn took considerably longer in some areas than in other s. This discrepancy was the reason for defining growing egree-days .Hence in humid lowa where summer nighttime temperatures are high growing degree-days accumulate much faster. Consequently the corn matures in consid erably fewer days than in the drier west where summer nighttime temperetures are lower and each day accumulates fewer growing degree –days .Although moisture and other condition are not taken in to account grow ing degree –days nevertheless serve as a useful in .

90/2/2::: 5:29 ع

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64 هستش

NA.GH

When the weathercaster reports that the normal high temperature for today is 68 f does this mean that the high temperature on this day is usually 68 f Or does it mean that we should expect a high temperature near 68f actually we shold expect neither one. Remember that word normal or norm refers to weather data averaged over a period of 30year .for exampel fig 1shows the high temperature measured for 30 year in a southwestern city on march 15.the avrege (mean0high temperature for this period is 68 f hence the normal high temperature for this data is 68 f (dashed line).Natice howener that only on one day during this 30-year period did the high temperature actually measure 68 f (large red dot).In fact the most common high temperature (called the mode0was 60f and occurred on 4days (blue dost0) .So what be considered a typical high temperature for this date Actually ;ony high temperature that lies between about 47 f and.FIGURE 1 /The high temperature measured (for 30years)on march 15 in a city located in the south western United states. The dashed line the normal temperature for the 30-year period. 89 f (two standard deviations*on either side of 68 f would be consid ered typical for this day.)While a high temperature of 80 f may be quite warm and a high temperature of 47 f may be quit cool they are both no more uncommomn (unusual) that a high temperature of 68 Which is the normal high temperature for the 30year period.This same type of reasoning applies to normal rainfall as the actual amount of precipitation will likely be greater or less than the 30-year average. Temperatures throughout the year are quit similar .However often this is not the case. For exampel san; farncisco; california and Richmond Virginia are at the same latitude (37 n) . Both have similar hours of daylight during the year Both have the same mean an nual temperature -14 c (57 f) . Here the similarities end.The temperature differences between the two cities are apparent to anyone who has traveled to san farn cisco during the summer weather in Richmond. Figure 3.11summarizes the average temperature for san francisco and richmond . Notice that the coldest month for both cities is January .Even though Januarey in Richmond averages only 8 c (14 f ) colder than January in san Francisco people in Richmond awaken an average January minimum tempeerature of -6 c (21 f) which is much colder than the lowest temperature ever recorded in san Francisco. Trees that thrive in san francisco;s weather would find it difficult surviving a winter in Richmond .So even though san franciso and Richmond have the same mean annual temperature the behavior and rang of thire temperatures differ greatly.

90/2/2::: 5:28 ع

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63 هستش

NA.GH

In humid regions the diurnal temperature rage is usullly small. Here haze and clouds lower the maxi mum temperature by preventing some of the sun;s energy from reaching the surface.at night the moist air keeps the minimum temperature high by absorbing the eart;s infared radiating a portion of it to the ground.An example of a humid city with a small summer diurnal temperature rang is charleston south carolinwhere the average july maximum is tempeerature is 32(72f0and the (90 f) the average minimum is 22 (72 f) and the diurnal range is only 10 (18 f).cities near larg bodies of water typically have smaller diurnal temperature ranges than cities further inland.This phenomenon is caused in part by the additional water vapor in the air and by the fact that water warms and cools much more slowly than land. Moreover cities whose temperature reading are obtained at airports often have larger diurnal temperature ranges than those whoes readings are obtained in downtown areas.the reason for this fact is that night time temperatures in cities .this nighttime city warmth –called the urban hest island –is due to industril and urban development a topic that will be treated more completely in chapter12. The average of the highest and lowest temperature for a 24-hour period is known as the mean dail temperature.most newspapers list the mean dialy temperature along with the highest and lowest temperatures for the preceding day.The average of the mean daily temperatures for a particular date averaged for a 30-year period give the average temperature for each month is the average of the daily mean temperatures for that month .An ditional information on the concept of normal temperature of the warmest and coldest months is called the annual range of temperature .usually the largest an nual ranges occur over land the smallest over water .Hence inland cities have larger annual ranges than coastal cities. Near the equator (because daylight length varies little and the sun is always high in the noon sky)annual temperature ranges are small usually less than 3 (5 f0.Quito Ecuador –on the equator at an elevation of 2850m(9350ft)-experiencese an annual range of less than 1.in middle and high latitudes large seasonal variations in the amount of sunlight reaching the surface produce larg temperature contrasts between winter and summer.Here annual ranges are larg espe.one of the greatesttemperature ranges ever recorded in the Norhern Hemisphere (56 c or 100 f)occurred at browning Mantana on january 23;1916 when the air temperature plummeted from 7 c (44 f)to 49 c (-56 f)in less than 24houres.this huge temperature range howewer would represent a rather typical day on the plant Mars where the average high temperature reaches about -12 c(10 f)and the average low drops to -79 c (-110 f)producing a daily temperature range of 67 c;or 120 f . Cially in the middle of a continent .Yakutsk in north eastern Siberia near the arctic circle has an extremely larg annual temperature range of 62 c(112 f).The average temperature of any station for the entire year is the mean (avrege0annual temperature which represents the average of the twelve monthly average temperatures .*When two cities have the same mean annual temperature it might first seem that their .*The mean annual temperature may be obtained by taking the of the 12 monthly means and dividing that total by 12;or by obtaining the sum of the daily mean and dividing that total by 365.

90/2/2::: 5:27 ع

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پیامهای عمومی ارسال شده

+ با مشت بسته چشم گشودی در این جهان / یعنی به غیر حرص و غضب نیست حالیم/ با مشت باز نیز روی آخر به زیر خاک / یعنی ببین که میروم و دست خالیم!!!!(شهریار)

+ من امشب برای نخستین بار گریه میکنم /گرانبهاتر از اشک در دامان طبیعت هیچ نیست تا گرانبهاترین چیزها را از انسان نگیرد/ تقدیم به آقای siah poosh

+ در 16 سالگی هنوز بچه ای / در 17 سالگی طعم آزادی را میچشی /در 18 سالگی امضاء تو قانونی است / در 19 سالگی از این همه فرازو نشیب تازه میفهمی خیلی از مرحله پرتی....

+ قایقی خواهم ساخت خواهم انداخت به آب دور خواهم شد از این خاک غریب که در آن هیچ کسی نیست که قهرمانان را در بیشه ی عشق بیدار کند(سهراب سپهری)